Updates:

* Moved dictobject.c:unicode_eq() to unicodeobject.c:_PyUnicode_Eq()
* Added another optimization step to _PyUnicode_Eq(). The hash is
required later anyway and comparing two hashes is much faster than
memcmp-ing the unicode objects.
    if (unicode_hash(a) != unicode_hash(b))
        return 0;
* Factored out the ((PyUnicodeObject *) v)->hash optimization into a
function object.c:_PyObject_HashFast() which does the trick for
PyUnicode and PyString. The trick was used a couple of times in
dictobject.c and setobject.c. We may even think about moving the trick
to PyObject_Hash() directly.